Optical switches serve numerous purposes within an optical network. Each such application has its own required time of reaction, and these reaction times vary over about eight orders of magnitude. Four applications are of special interest today. A first application is provisioning, wherein switches are used inside optical cross-connects for reconfiguring to support or define a new light path. This type of switch typically replaces a mechanical switch or a fiber patch panel, with a leisurely required switching times of 1-10 msec. A second application is protection switching, used to switch optical data traffic from a first primary fiber to a second primary fiber, where the first fiber has failed or otherwise malfunctions. Because such a switch typically operates between two such primary fibers, in a 2×2 array, the required switching times are of the order of hundreds of μsec.
A third application is packet switching, driven in part by a migration of voice to data processing channels. Such switches are important in high speed (OCn, with n≧12) networks that switch individual optical packets, with required switching times that are smaller than a typical packet duration. For example, a 53-byte ATM packet at 10 Gbps is 42 nsec in duration and requires a packet switching time of no more than 5-10 nsec. A fourth application is external on/off modulation, with a required switching time that is a small fraction of bit duration (e.g., 100 psec for a 10 Gbps data stream).
Switching times for the first and second applications can be reasonably met with currently available technology, but the third and fourth applications require switching times and associated reliabilities that are not yet achieved. What is needed is an optical switch that can switch a light beam having a selected wavelength between a first optical path and a second optical path in a time interval between a few milliseconds and a few nanoseconds and that can reliably provide this switching for each of several selected wavelengths. Preferably, this switching should be reproducible and should quickly respond to change of at most one or two parameters.